Exhaust system of an internal combustion engine

ABSTRACT

An exhaust system of an internal combustion engine, in particular of a vehicle, has an insert through which exhaust gas flows, for purifying the exhaust gas, and a mixing chamber through which exhaust gas flows and which is arranged upstream of the insert through which exhaust gas flows. The mixing chamber includes at least one permeable wall and is arranged on a channel wall of the exhaust system and protrudes radially into the interior of the exhaust system. The exhaust system further has a vaporizer device that vaporizes an oxidizable liquid and introduces the vapor into the mixing chamber, and an ignition device that protrudes at least partly into the mixing chamber. The vaporizer device includes a glow element which is configured and heatable in such a way that an auto-ignition of the oxidizable vapor occurs on its surface.

RELATED APPLICATION

This applications claims priority to German application 10 2008 062479.9, which was filed Dec. 16, 2008.

BACKGROUND OF THE INVENTION

To purify exhaust gases, vehicle exhaust systems have inserts, forexample catalytic converters or diesel particulate filters havingcatalytic converters connected upstream. Particulate filters requireregeneration at regular intervals. To reach the high temperatures thatare required for the regeneration, in most cases the particulate filterhas an oxidation catalytic converter connected upstream thereof in whichthe temperature of the exhaust gas is raised. For regeneration it isknown to introduce vapor upstream of the particulate filter, the vaporacting as a regeneration agent.

However, oxidation catalytic converters become active only as of aparticular temperature, which is not reached during a cold start and inthe starting phase of the engine. Increased pollutant values are knownto occur in this phase.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide an exhaust systemwhich operates effectively in the warm-up phase of the engine as well.In particular, the exhaust system according to the invention is intendedto allow a regeneration of the diesel particulate filter at lowertemperatures.

According to the invention, an exhaust system of an internal combustionengine, comprises a channel, an insert for purifying exhaust gas withinthe channel, a mixing chamber arranged upstream of the insert, avaporizer device vaporizing an oxidizable liquid and introducinggenerated oxidizable vapor into the mixing chamber, and an ignitiondevice protruding at least partly into the mixing chamber. The exhaustgas flows along the channel through the insert and the mixing chamber.The mixing chamber includes at least one permeable wall and is arrangedon a channel wall and protrudes radially into an interior of the exhaustsystem. The vaporizer device includes a glow element which is heatablein such a way that an auto-ignition of oxidizable vapor occurs on asurface of the glow element.

The combination of the vaporizer device with the ignition devicenecessitates no additional ignition elements, which reduces themanufacturing expenditure. Since the oxidizable liquid is igniteddirectly during or immediately upon the vaporizing process, a reliableignition is additionally ensured.

Furthermore, the invention provides an exhaust system of an internalcombustion engine, comprising a channel, an insert for purifying exhaustgas within the channel, a mixing chamber arranged upstream of theinsert, a vaporizer device vaporizing an oxidizable liquid andintroducing generated oxidizable vapor into the mixing chamber, and anignition device protruding at least partly into the mixing chamber. Theexhaust gas flows along the channel through the insert and the mixingchamber. The mixing chamber includes at least one permeable wall and isarranged on a channel wall and protrudes radially into an interior ofthe exhaust system. The ignition device includes at least one ignitionelectrode producing an ignition spark for ignition of the oxidizablevapor.

The oxidizable liquid or a mixture of the vaporized oxidizable liquidand exhaust gas is ignited still inside the mixing chamber before theoxidizable vapor is fed into the exhaust gas channel or into the insert.An ignition spark reliably ensures an ignition of the oxidizable vapor.

The ignition electrodes may be arranged, for example, on a channel wallsection which is located radially opposite to the mixing chamber. Inthis way, the ignition electrodes are arranged outside the mixingchamber and merely protrude into the mixing chamber. This means that theelectrodes can be manufactured separately and are so compact as to bepositionable in the region of the vaporizer device.

The electrodes employed in this embodiment may be, for example, sparkplugs as are commonly used in the automotive sector, which results inreduced manufacturing expenditure and production costs.

In one example, openings are provided on the channel wall of the exhaustsystem, with the spark plugs protruding through the openings and intothe gas guiding channel. The spark plugs may be secured to rims of theopenings, for example by a thread provided in each opening or byseparate fastening elements. In this way, the spark plugs may beinstalled or replaced in a simple manner.

To produce a larger or longer ignition spark, the ignition spark mayalso be produced between two electrodes. This allows the size or lengthof the ignition spark to be ensured and varied to achieve an improvedand reliable ignition effect.

In addition, the arrangement of the electrodes in the mixing chamberallows the ignition spark to be ideally oriented relative to an inflowdirection of the oxidizable liquid, so that a more effective ignitionoccurs. In one example, the electrodes are arranged such that theignition spark is oriented substantially transversely or perpendicularlyto the inflow direction of the oxidizable liquid into the mixingchamber.

In one example, an electronic controller is provided for the ignitiondevice and/or the vaporizer device. The electronic controller on thevaporizer device allows both the amount of the oxidizable liquid andalso the temperature of the vaporizer device to be regulated, so thatconsumption of the oxidizable liquid can be controlled. In addition, anelectronic controller for the ignition device permits a generation of anignition spark as needed, so that the exhaust system can be operatedmore effectively.

The electronic controller drives the ignition device and/or thevaporizer device depending on the temperature and/or the exhaust gasflow, for example. The amount of the oxidizable vapor can be regulatedsuch that the exhaust gas temperature is maintained in a temperaturerange that is ideal for the regeneration of the insert. When thetemperature in the gas guiding channel is sufficiently high, theelectronic controller can reduce the supply of the oxidizable vapor and,where required, suspend the ignition of the oxidizable vapor or, in casethe temperature is too low, can supply the oxidizable vapor and/oractivate the ignition. The exhaust gas flow may likewise be made use ofas an indicator for the electronic controller, since a higher exhaustgas flow occurs in the case of higher speeds and higher exhaust gastemperatures resulting therefrom.

The electronic controller controls more particularly the quantity of thevapor introduced into the mixing chamber as a function of thetemperature and/or the exhaust gas flow. The quantity of the oxidizablevapor allows the combustion in the exhaust system and, hence, theexhaust gas temperature to be controlled especially effectively, so thatthe ideal temperatures for a regeneration are always reached in theexhaust gas flow.

In one example, the vaporizer device includes a glow element, inparticular a glow plug, which terminates in the region of, or in, themixing chamber. The glow element produces the high temperatures that arenecessary for a vaporization of the oxidizable liquid.

In one example, the glow element can be heated to differenttemperatures. The glow element can be heated to a first temperaturelevel which ensures a vaporization of the liquid, and a secondtemperature level which leads to an auto-ignition of the vapor. As aresult, only one component is required for vaporizing the liquid and forigniting the vapor.

The insert of the exhaust system includes a diesel particulate filter,and an oxidation catalytic converter, for example, is arranged in theflow direction upstream of the diesel particulate filter. The catalyticconverter may also be dispensed with; in that case, the particulatefilter would be burnt free upon ignition of the vapor.

The vaporized liquid may, for example, be a fuel, in particular a dieselfuel.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of an exhaust system according to theinvention;

FIG. 2 shows a sectional view of the exhaust system according to theinvention in the region of the vaporizer device; and

FIG. 3 shows a perspective view of the exhaust system from FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates an exhaust system of an internal combustion engine,in particular of an internal combustion engine of a motor vehicle.Reference numeral 2 denotes an exhaust gas-carrying pipe thataccommodates a diesel particulate filter 4. Arranged in the dieselparticulate filter 4 is a body 6 through which exhaust gas flows andwhich is also known as a substrate or insert and constitutes the filterbody. Positioned upstream of the diesel particulate filter 4 is anoxidation catalytic converter 8 which may be applied onto the substrateof the filter body or may be configured as a separate body.

The wall of the pipe 2 constitutes a channel wall 12 of the exhaustsystem 10, which in its interior defines a gas guiding channel 14.

Provided upstream of the diesel particulate filter 4 is a vaporizerdevice 16 and, optionally, an ignition device 18 which is likewisearranged in the region of the vaporizer device 16 in the gas guidingdirection.

As can be seen in section according to FIG. 2, the vaporizer device 16and the ignition device 18 are attached to the channel wall 12.

Arranged in the gas guiding channel 14 is a mixing chamber 20 which isdefined by a cylindrical wall 22 which is fastened to the channel wall12 and has openings 23 on its entire peripheral surface, so that theexhaust gas can flow through the mixing chamber (see in particular FIG.3).

The ignition device 18 is fastened to a wall section of the channel wall12 radially opposite to the mixing chamber 20 and has a free end thatprotrudes into the mixing chamber 20, as does the vaporizer device 16.

The vaporizer device 16 has a glow element 24 and a feed line 26 throughwhich an oxidizable liquid is fed to the glow element 24. The oxidizableliquid is vaporized by the glow element 24 and reaches the mixingchamber 20 in an axial inflow direction E.

In the mixing chamber 20 the vaporized liquid is mixed with the exhaustgas flowing through. At a sufficiently high temperature, the oxidizablevapor burns with the residual oxygen contained in the exhaust gas andthus raises the temperature of the exhaust gas, so that the oxidationcatalytic converter 8 that is arranged downstream of the vaporizerdevice 16 in the flow direction is heated to the operating temperature.

An ignition of the oxidizable liquid or of the oxidizable vapor may beeffected by the ignition device 18 protruding into the mixing chamber20. The ignition device 18 has two spark plugs 28 in this example, whicheach protrude into the mixing chamber 20 by an electrode 30. The sparkplugs 28 are each secured in an opening 32 in the channel wall 12 andeach protrude into the mixing chamber 20 by an electrode 30. When thecatalytic converter is heated up, an ignition spark Z, which is orientedtransversely to an inflow direction E, will be generated between theelectrodes 30. The ignition spark ignites the oxidizable vapor or themixture consisting of oxidizable vapor and exhaust gas.

Activation of the ignition device 18 may be effected here by anelectronic controller which checks, for example, a temperature of theexhaust gas and, when the temperature is not sufficient for aregeneration, drives the ignition device 18, so that the ignition sparkZ is produced. The controlling process may, however, be effected also asa function of other measured variables, such as, e.g., the exhaust gasflow. But embodiments without an electronic controller are alsoconceivable.

Provision is further made for the vaporizer device 16 to have acontroller which regulates the supply of the oxidizable liquid as afunction of the exhaust gas temperature, for example. The controller maylikewise regulate the temperature of the glow element 24 and in this waycontrol the vaporizing quantity of the oxidizable liquid.

The spark plugs 28 of the ignition device 18 are each arranged in anopening 32 and each protrude into the mixing chamber 20 by an electrode30. This allows the spark plugs 28 to be quickly replaced. But the sparkplugs 28 may also be arranged on the exhaust system 10 in any other way.

Instead of the spark plugs 28 shown here, other electrodes 30 may alsobe used. In particular, it is also possible to provide only one sparkplug 28 having two electrodes 30.

The electrodes 30 may protrude into the mixing chamber 20 in any desiredmanner to produce an ignition spark Z. In particular, the ignition sparkZ need not be oriented transversely to the inflow direction E of theoxidizable liquid.

The ignition device 18 need not necessarily be arranged on a section ofthe channel wall 12 located radially opposite to the mixing chamber 20.The ignition device 18 may be arranged on the exhaust system 10 in anydesired way. In particular, it is conceivable for the ignition device 18to be arranged on, or integrated in, the vaporizer device 16.

The shape and the size of the mixing chamber 20 may likewise be variedas desired, just as the openings 23 on the wall 22 of the mixing chambermay be varies. More particularly, the mixing chamber 20 need not be of acylindrical design.

Rather than by the ignition device 18, the ignition of the oxidizablevapor may also be effected by the vaporizer device 16. In this case, theignition will be effected by the glow element 24, which is heatable tosuch an extent that an auto-ignition of the oxidizable vapor occurs onits surface. To this end, the glow element 24 is heated to differenttemperature levels, for example, on the one hand for the vaporizationand, on the other hand, for vaporization and subsequent auto-ignition ofthe vapor/gas mixture at the end of the glow element 24. In thisembodiment, the ignition devices 18 may optionally be dispensed with.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this invention. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this invention.

1. An exhaust system of an internal combustion engine, comprising: achannel; an insert for purifying exhaust gas within said channel; amixing chamber arranged upstream of said insert; a vaporizer devicevaporizing an oxidizable liquid and introducing generated oxidizablevapor into said mixing chamber; and an ignition device protruding atleast partly into said mixing chamber, said exhaust gas flowing alongsaid channel through said insert and said mixing chamber, said mixingchamber including at least one permeable wall and being arranged on achannel wall and protruding radially into an interior of said exhaustsystem, and said vaporizer device including a glow element heatable insuch a way that an auto-ignition of oxidizable vapor occurs on a surfaceof the glow element.
 2. The exhaust system according to claim 1, whereinsaid ignition device includes one or more ignition electrodes producingan ignition spark for ignition of the oxidizable vapor.
 3. An exhaustsystem of an internal combustion engine, comprising: a channel; aninsert for purifying exhaust gas within said channel; a mixing chamberarranged upstream of said insert; a vaporizer device vaporizing anoxidizable liquid and introducing generated oxidizable vapor into saidmixing chamber; and an ignition device protruding at least partly intosaid mixing chamber, said exhaust gas flowing along said channel throughsaid insert and said mixing chamber, said mixing chamber including atleast one permeable wall and being arranged on a channel wall andprotruding radially into an interior of said exhaust system, and saidignition device including at least one ignition electrode producing anignition spark for ignition of said oxidizable vapor.
 4. The exhaustsystem according to claim 3, wherein said at least one ignitionelectrode is arranged on a channel wall section located radiallyopposite to said mixing chamber.
 5. The exhaust system according toclaim 3, wherein said at least one ignition electrode is a spark plug.6. The exhaust system according to claim 5, wherein at least one openingis provided on said channel wall of said exhaust system, said at leastone spark plug protruding through said at least one opening into a gasguiding channel.
 7. The exhaust system according to claim 3, whereinsaid ignition spark is produced between two electrodes.
 8. The exhaustsystem according to claim 7, wherein said ignition spark is in one of asubstantially transverse and perpendicular orientation to an inflowdirection of said oxidizable liquid into said mixing chamber.
 9. Theexhaust system according to claim 1, including an electronic controllerfor at least one of said ignition device and said vaporizer device. 10.The exhaust system according to claim 9, wherein said electroniccontroller drives at least one of said ignition device and saidvaporizer device for igniting said vapor depending on at least one of atemperature and exhaust gas flow.
 11. The exhaust system according to 9,wherein said electronic controller means controls the quantity of saidvapor introduced into said mixing chamber as a function of at least oneof a temperature and exhaust gas flow.
 12. The exhaust system accordingto claim 1, wherein said vaporizer device includes a glow element. 13.The exhaust system according to claim 12, wherein said glow elementterminates in a region of, or in, said mixing chamber.
 14. The exhaustsystem according to claim 12, wherein said glow element can be heated todifferent temperatures, said different temperatures including at least afirst temperature level which ensures a vaporization of said oxidizableliquid and a second temperature level which leads to an auto-ignition ofsaid vapor.
 15. The exhaust system according to claim 1, wherein saidinsert includes a diesel particulate filter.
 16. The exhaust systemaccording to claim 15, wherein an oxidation catalytic converter isarranged in said insert in a flow direction upstream of said dieselparticulate filter.
 17. The exhaust system according to claim 1, whereinsaid oxidizable liquid is a fuel.